Field of the Disclosure
Embodiments of the disclosure relate to a touch screen sensing device and a method for sensing a touch screen.
Discussion of the Related Art
A user interface (UI) is configured so that users are able to communicate with various electronic devices and thus can easily and comfortably control the electronic devices as they desire. Examples of the user interface include a keypad, a keyboard, a mouse, an on-screen display (OSD), and a remote controller having an infrared communication function or a radio frequency (RF) communication function. User interface technologies have continuously expanded to increase user's sensibility and handling convenience. A touch UI, a voice recognition UI, a 3D UI, etc. have been recently developed as the user interface.
The touch UI has been necessarily used in portable information appliances and has been expanded to the use of home appliances. There is a mutual capacitance touch screen as an example of a touch screen for implementing the touch UI. The mutual capacitance touch screen has been spotlighted because it can perform the sensing of proximity input as well as the sensing of touch input and also can recognize respective touch locations of a multi-touch (or multi-proximity) operation.
A method for sensing the touch screen includes supplying a driving voltage to touch sensors of the touch screen to generate charges from a mutual capacitance of the touch sensors, converting a charge change amount of the mutual capacitance into a voltage change amount, and comparing a voltage change amount before and after a touch operation with a reference voltage or counting the voltage change amount. Other methods have been known. As a method for reducing an influence of a noise mixed in the touch sensors of the mutual capacitance touch screen, there is a method for removing DC offset included in the voltage of the touch sensor received using a digital-to-analog converter (DAC).
When the touch screen receives the voltage of the touch sensor through a Rx channel, the voltage of the Rx channel changes sensitively because of a parasitic capacitance between adjacent Rx channels. In the mutual capacitance touch screen, a signal-to-noise ratio (often abbreviated SNR or S/N) of a signal received through the Rx channel is reduced because of a common mode noise, for example, a driving signal of a display panel. The touch screen is easily affected by a radio frequency noise received from the display panel or other peripheral elements. The radio frequency noise applied to the Tx and Rx channels of the touch screen further reduces the signal-to-noise ratio of the signal received through the Rx channel. Thus, the related art method for sensing the touch screen may wrongly recognize the touch input or may hardly recognize the accurate touch position because of the parasitic capacitance of the touch screen and the low signal-to-noise ratio.